Surfactants are the single most important cleaning ingredient in cleaning products. Environmental regulations, consumer habits, and consumer practices have forced new developments in the surfactant industry to produce lower-cost, higher-performing, and environmentally friendly products. Examples of developments in the surfactant industry are described by J. Scheibel in the Journal of Surfactants and Detergents, “The Evolution of Anionic Surfactant Technology to Meet the Requirements of the Laundry Detergent Industry,” volume 7, number 4, October, 2004 (“Scheibel JSD Article” hereinafter), which is incorporated herein by reference. Today, challenges facing the surfactant industry include colder wash temperatures, less efficient builders, liquid products without calcium control, and a push for reduced surfactant use overall because of the perceived environmental impact of surfactants.
Alkylphenyl sulfonates are surfactants derived from tetrapropylene that have very complex branching structures (e.g., 3 or 4 branches per molecule). The structure below illustrates one example of a hard alkylphenyl sulfonate molecule, which has branching near the polar head group and in the middle of the surfactant.

ABS surfactants were prominent until the early 1960s when they were subjected to environmental regulations for being poorly biodegradable. Alkylphenyl sulfonate surfactants were then replaced with the readily biodegradable linear alkylphenyl sulfonate (LAS) surfactants, which are easily obtainable and currently in use today. Use of LAS surfactants and other similar linear surfactants is limited because they have poor solubility in cold water and hard water conditions. In fact, more than half of the LAS detergent in products may be lost during use due to the formation of multilayered vesicles that resemble large onion-like structures. Formulators can increase the solubility of linear surfactants, for example, by introducing cosurfactants or by using linear alcohol ethoxylated sulfates (AES). However, AES surfactants have lower surface activity, as well as lower mass efficiency than LAS surfactants. Further, the use of cosurfactants or AES surfactants limits formulation flexibility and can add substantial cost to the detergent. ABS, LAS, and AES surfactants are described in detail in the Scheibel JSD article.
Surfactants with light, mid-chain branching, such as highly soluble alcohol sulfate (HSAS) surfactants derived from petroleum feedstocks, were then developed for use in consumer products. HSAS surfactants are illustrated in the Scheibel JSD article, as well as U.S. Pat. Nos. 6,020,303; 6,060,443; and 6,335,312; and U.S. Patent Application Publication No. 2010/0137649, each incorporated herein by reference. The structure below illustrates one example of a HSAS surfactant, showing a single methyl branch near the mid-point of the surfactant.

Although the HSAS surfactants provide good cleaning ability in cold and hard water, have high solubility, good grease removal properties, and good biodegradability, too much branching prevents them from packing efficiently at the air-water interface. Also, if the total carbon chain length is too long, insufficient foam volume will be generated because bubble size will be greatly diminished. These two factors can severely limit the foamability of the technology. In some cases foamability and stability of foam are critical to the consumer goods application, such as in dishwashing liquids, hand wash detergents, and shampoos.
U.S. Pat. No. 6,306,817, incorporated herein by reference, describes alkylphenyl sulfonates that have light chain branching on their alkyl groups. According to the disclosure, these surfactants have superior cold water solubility, for example, for cold water laundering; superior hardness tolerance; and excellent detergency, especially under low temperature wash conditions. These surfactants also provide reduced build-up of old fabric softener residues from fabrics being laundered, and improved removal of lipid or greasy soils from fabrics.
U.S. Pat. No. 6,566,319, incorporated herein by reference, describes a method of making a mixture of C11-C14 alkylphenyl sulfonates using alkene feedstocks having particular chain lengths (e.g., an alkene feedstock with a total of 5, 6, and 7 carbon atoms, an alkene feedstock with a total of 5 and 7 carbon atoms, an alkene feedstock with a total of 6 and 7 carbon atoms, an alkene feedstock with a total of 6 or 7 carbon atoms). The process of the '319 patent is advantageous because it allows some degree of control over the chain length of the alkyl group on the alkylphenyl sulfonate. The method does not allow for specific alkyl chain distributions of the alkylphenyl sulfonate or for renewable alkylphenyl sulfonates.
Accordingly, it would be desirable to find detergent formulations that deliver even better performance and better value to the consumer, and to produce these formulations simply, efficiently, and in a controlled, cost effective manner. In view of the very large tonnages of alkylphenyl sulfonate surfactants and detergent formulations used worldwide, even modest improvements in performance of the basic alkylphenyl sulfonate detergent would have a significant impact.